The present invention relates to a control arrangement for a hydraulic drive or servomotor. More particularly, it relates to an arrangement for a hydraulic drive or servomotor with a control slider which during its raising controls a pressure medium from an adjustable pressure medium supply device via an unblockable check valve to the motor, and during lowering releases the same to a container.
Control arrangements of the above-mentioned general type are known in the art. One such control arrangement is disclosed, for example, in the German Auslegeschrift No. 1,938,896. It serves for controlling a lifting mechanism of a tractor, wherein the control slider is constantly adjustable via a mechanical adjusting linkage. For raising the motor of the lifting mechanism load-independently and in a proportional manner, the control slider cooperates with a reverse valve formed as a three-way flow regulating valve, whereby also in a neutral position of the control slider the neutral reverse pressure can be maintained relatively low. During lowering of the lifting mechanism the control slider must control an unblockable return valve which protects the motor. The disadvantage of this arrangement is that it is relatively expensive inasmuch as for controlling of the simply operating motor two motor chambers are required from which the respective conduits lead to the unblockable check valve. Moreover, there is the disadvantage that the reverse pressure in the neutral position of the control slider must be selected so high that in the lowered position the check valve can unblock. In addition, for a reliable functioning of the mechanically controlled proportionally operating control arrangement, an additional auxiliary slider is required in the main control slider with which a process identified as a fixed throttling is eliminated. This auxiliary slider results, however, in an expensive construction.